There are five types of mass filters/analyzers used commercially today in mass spectrometry:
(1) sector (magnetic and electric types);
(2) quadrupole;
(3) ion cyclotron resonance;
(4) ion trap; and
(5) time-of-flight.
Generally, time-of-flight mass filters offer fast analysis times in comparison with the other types of mass filters, however they are not intrinsically able to generate high resolution spectra. Generally, sector mass filters equipped with an array detector are able to generate high resolution spectra, however they are costly and large. Thus, there is a need to develop an instrument that offers the advantages of both of these types of instruments, including fast analysis time and high resolution spectra, without the attendant disadvantages, namely high cost and high space requirements.
U.S. Pat. No. 3,953,732 discloses a mass spectrometer and a method of mass spectrometry including the steps of:
(1) projecting a beam of particles which have a wide range of kinetic energy into an analyzing region; PA1 (2) applying an electric field in the analyzing region in a direction transverse to the direction of the beam to deflect the particles in the beam independently of their initial kinetic energy as they enter the analyzing region along paths of length which are dependent upon the mass and charge of the particles; and PA1 (3) collecting the deflected particles at points spaced along the analyzing region from the entry of the beam in the analyzing region. PA1 (1) an ion source which generates nearly monoenergetically-pulsed ion packets which spatially focus at a predetermined distance along the drift path of the ions in the mass filter/analyzer; PA1 (2) a mass filter/analyzer containing: PA1 T.sub.on =time-dependent electric field turn-on time PA1 (3) a spatial mass detector located at the end of the deflection region of the mass analyzer/filter and orthogonal to the ion source.
The method applies a time-dependent electric field which varies monotonically as an inverse function of time for the projection period to the particles which have a wide range of kinetic energy.
U.S. Pat. No. 5,420,423 discloses a mass spectrometer containing an ion source and a channel plate detector connected via a flight tube. Dispersion electrodes are positioned between the ion source and the detector. Shielding electrodes are placed closely to the dispersion electrodes to act as aperture lenses and shields of the electric field. As ion packets travel from the ion source toward the detector passing through the shielding electrodes and the gap between the dispersion electrodes, a dynamically-varying electric field is applied to the ion packets to deflect the ions according to their mass-to-charge ratio.